The objective of this project is to study cell-mediated immune responses of monkeys immunized with Streptococcus mutans, and humans with or without caries and periodontal disease. Human or monkey blood lymphocytes were separated on Ficoll-Hypaque and the optimal responses to mitogens like PHA, Con A, SLO and staphlococcal lysate were determined. The optimal culture conditions in terms of cell density, time incubation, use of different sera for detecting lymphoproliferative response to various S. mutans derived antigens have been established.